The problem of (with) authenticity

It seems to me that many questions about photography - like, for example, the one just discussed by Shane - boil down to the complex of authenticity. I find it quite interesting to see how many people still want a photograph to be absolutely authentic. It has to depict something that really happened or that really exists that way. So “street photography” is taken as more authentic (or honest) than, say, staged photography (a variant of this is the “reality TV” craze, which shows “real” people and their “real” problems). I really don’t know how useful such an approach to photography is. If we were to make authenticity our criterion for what is good and bad photography, we would limit our experience of photography as an art form quite severely.